It is well known in motor vehicles to utilize a seat belt for restraining a seated occupant. The belt is attached to a retractor having a belt reel rotatably mounted on a retractor housing by a reel shaft. The reel shaft has one end connected to a spiral spring to bias the reel in a direction to wind up the belt. The other end of the reel shaft typically carries a toothed sprocket which is engageable by a locking pawl to lock the reel shaft against rotation in the belt unwinding direction. The locking pawl is typically operated by an inertia sensing mechanism which may be a pendulum or an inertia switch coupled to an electrical actuator such as a solenoid.